The invention relates to delivery of drugs to a desired location within the body.
Systemic administration of drugs treats the organism as a whole, even though the disease may be localized, such as occlusion of a duct or vessel. When administered to a patient systemically, many drugs, e.g., chemotherapeutic drugs such as those used to treat cancer and benign prostate hyperplasia, cause undesirable side effects. Localization of a drug poses special problems in cases involving the walls of ducts and vessels, since, by nature, these organs serve as transport systems.
Artherosclerotic disease, for example, causes localized occlusion of the blood vessels resulting from the build-up of plaque. As the deposits increase in size, they reduce the diameter of the arteries and impede blood circulation. Angioplasty, which involves the insertion of catheters, such as balloon catheters, through the occluded region of the blood vessel in order to expand it, has been used to treat artherosclerosis.
The aftermath of angioplasty in many cases is problematic, due to restenosis, or closing of the vessel, that can occur from causes including mechanical abrasion and the proliferation of smooth muscle cells stimulated by the angioplasty treatment. Restenosis may also occur as a result of clot formation following angioplasty, due to injury to the vessel wall which triggers the natural clot-forming reactions of the blood.
The invention features a method for delivering a drug to tissue at a desired location within the body comprising the following steps: providing a catheter constructed for insertion in the body, a portion of which carries a hydrogel having the capacity to incorporate a predetermined substantial amount of a drug which is substantially immobilized in the hydrogel until released by a triggering agent or condition that differs from ambient physiological conditions; introducing the catheter to the body to the point of desired drug application; and exposing the hydrogel to the triggering agent or condition. Exposure of the hydrogel to the triggering agent or condition triggers release of the drug from the hydrogel for delivery to the desired location within the body.
The invention also features a method for triggering release of a drug from a hydrogel to a tissue at a desired location of the body using a balloon catheter such as a non-vascular or vascular catheter, e.g., an angioplasty catheter. The balloon portion of the catheter is coated on its outer surface with a hydrogel having the capacity to incorporate a predetermined substantial amount of drug which is substantially immobilized in the hydrogel until released by a triggering agent or condition which is different from ambient physiological conditions. Preferably, the catheter has a porous balloon portion, e.g, a balloon with channels or pores through which a solution containing a triggering agent can pass and come in contact with the hydrogel. The invention also includes a kit for triggering release of a drug from a hydrogel-coated drug delivery catheter and a catheter for triggered drug delivery.
The method of triggered drug delivery includes the following steps: providing a catheter constructed for insertion in the body with a catheter shaft having an expandable hydrogel-coated porous balloon portion mounted on the catheter shaft which is expandable to engage the tissue at a controlled pressure to fill a cross-section of the body lumen and press against the body lumen wall; introducing the catheter to the body lumen wherein the balloon portion is positioned at the point of desired drug application; expanding the balloon portion to engage the tissue; and infusing the triggering agent into the hydrogel. Upon contact of the triggering agent with the hydrogel, the drug is released at the desired location of the wall of a body lumen.
Following release of the drug from the hydrogel coating, the hydrogel coating may be replenished with an additional dose of drug delivered to the hydrogel from the catheter through pores or channels in the porous balloon portion. The drug contacts the hydrogel and becomes immobilized in the hydrogel until a subsequent delivery of triggering agent to the hydrogel, which in turn, triggers release of the additional dose of drug. This process of replenishment of hydrogel with drug and triggered release may be repeated as many times as desired.
The drug to be delivered is associated with the hydrogel by covalent, ionic or hydrogen bonding. Preferably, the associations are ionic interactions, and the triggering agent increases local ionic strength causing release of the drug from the hydrogel. A change in ionic strength may also affect the hydrogel itself, causing a volume phase transition, e.g., an expansion or contraction, of the hydrogel, thus triggering release of the drug. The drug may also be associated with the hydrogel by hydrogen-bonding, and the drug released by a change in pH.
The drug may be cationic and the hydrogel anionic. Alternatively, the drug may be anionic and the hydrogel cationic. In either situation, release of the drug is induced by contacting the hydrogel with a physiologically-acceptable saline solution, the ionic strength of which differs from that of ambient physiological conditions. The saline solution alters the ionic strength in the microenvironment of the hydrogel, thus triggering drug release. Preferably, the solution consists essentially of 0.2M to 5 M NaCl, more preferably 0.2M to 3.5 M NaCl, and most preferably 0.1 to 0.2M NaCl. In addition to a physiologically-acceptable saline solution, any salt solution may be used to trigger drug release, e.g., sodium phosphate, sodium bicarbonate, sodium citrate, potassium chloride, sodium sulfate, or sodium acetate. The solution may also contain inactive ingredients, e.g., buffering agents or preservatives.
A variety of drugs may be delivered using the claimed methods. The drug may be an anti-thrombogenic drug, such as heparin; low molecular weight heparin, e.g., ENOXAPRIN; aspirin; phe-L-pro-L-arginyl chloromethyl ketone (PPACK); hirudin, HIRULOG(copyright); Warfarin; Argatroban; or tissue factor pathway inhibitor (TPFI). The drug may also be a thrombolytic drug, such as urokinase; pro-urokinase; streptokinase; tissue plasminogen activator; anisolated plasminogen streptokinase activator complex (APSAC), e.g., EMINASE(copyright); an inhibitor of PAI-1, TA plasminogen; or cathepepsin D. Anti-platelet agents, such as chimeric 7E3 antibody (Reopro); Ticolpidine; Integrilin; TP9201; nitric oxide (NO) and derivatives thereof, e.g., protein-linked NO; Iloprost, or MK383, may be similarly delivered and triggered. Other drugs suitable for delivery in this manner include protein and polypeptide drugs, e.g., angiogenesis factors including but not limited to fibroblast growth factor (FGF), vascular endothelial growth factor (VEGF), transforming growth factor-beta, (TGFxcex2), platelet-derived growth factor (PDGF), epidermal growth factor (EGF), and urokinase. Other drugs to be delivered according to the invention include those to treat benign hyperplasia, e.g., PROSCAR(copyright), and HYTRIN(copyright). Other drugs include antiproliferative drugs, such monoclonal antibodies capable of blocking smooth muscle cell proliferation, e.g., anti-PDGF and anti-FGF; tyrosine kinase inhibitors, e.g., tyrophosphins, antisense oligonucletides to c-myc, c-myb; NO; gene encoding thymidine kinase (TK); fusion toxins, e.g, DAB389-EGF; immunotoxins, angiopeptin; antioxidant drugs, e.g., probudol, lovastatin, vitamin C and vitamin E; calcium channel blockers, e.g., nificitine, veratimil, ACE inhibitors, fofinopril and cilazapril. Chemotherapeutic drugs to treat various forms of cancer, e.g., HLB-7; granulocyte macrophage colony stimulating factor (GM-CSF); interferonxcex3; immunotoxins, e.g., BMS-18224801, and BR-96-DOX; ONCOLYSIN(copyright); fusion toxins, e.g., DAB389-IL-2, and DAB389-EGF; 5-Fluorouracil; methotrexate; and TAXOL(copyright). The drugs may be in any form capable of associating with the hydrogel and subsequently being released from the hydrogel by a triggering agent, including small molecules, proteins, polypeptides, and DNA encoding such protein or polypeptide drugs.
The immobilized drug to be delivered to a body tissue may also be released from the hydrogel by contacting the hydrogel with a solution having a pH which induces a volume phase transition of hydrogel. pH-sensitive polymers include poly(hydroxethyl)methacrylate-co-methacrylic acid) and a copolymer of M,N,dimethylaminoethyl methacrylate and divinyl benzene. For example, the solution may cause the hydrogel to swell, thus allowing the drug to diffuse out of the hydrogel. Alternatively, the solution may cause the hydrogel to contract, thereby squeezing the drug out of the hydrogel. The pH of the triggering solution is slightly above or below, e.g., 0.1 pH unit greater than or less than ambient physiological pH, i.e., pH 7.4. For example, the pH of the solution is preferably greater than about 7.5., e.g., in the range of 7.5 to 8.4, or less than about 7.3, e.g., in the range of 6.4 to 7.3. The pH of the solution may also be slightly above or below the optimal pH of the drug/hydrogel interaction. In addition to inducing a volume phase transition of the hydrogel, a change in pH can also be used to trigger release of a drug associated with a hydrogel by hydrogen bonding.
The invention also includes a method of triggered drug delivery in which a balloon portion of a catheter is inflated to a pressure condition that triggers release of said drug from the hydrogel. Preferably, the pressure condition is at least two atmospheres.
The invention also features a method for triggering release of a drug from a temperature-sensitive hydrogel which includes the steps of: providing a thermal catheter constructed for insertion in a body lumen with a catheter shaft having an expandable balloon portion coated with a temperature-sensitive hydrogel previously loaded with the drug to be delivered; introducing the catheter to the body to the point of desired drug application; expanding the balloon portion to engage the tissue; and applying heat to the temperature-sensitive hydrogel. An increase in temperature above body temperature, e.g., at least 1xc2x0 C. above ambient body temperature, triggers release of the drug at the desired location of the wall of a body lumen by inducing a volume phase transition of the hydrogel. In preferred embodiments, the temperature-sensitive hydrogel is a polyacrylic acid or derivative thereof, e.g., poly (N-isopropylacrylamide) gel, and the increase in temperature causes the hydrogel to contract, thereby forcing the drug out of the hydrogel. Alternatively, the temperature-sensitive hydrogel is an interpenetrating hydrogel network of poly(acrylamide) and poly(acrylic acid), and the increase in temperature causes the hydrogel to swell, thereby allowing the drug to diffuse out of the gel.
The temperature required for triggering release of the drug from the hydrogel is preferably between 1-80xc2x0 C. above ambient body temperature, e.g., 37xc2x0 C. More preferably, the temperature is between 1-50xc2x0 C. above body temperature, and most preferably, the temperature is between 1-5xc2x0 C. above body temperature, e.g. 38xc2x0 C.
Drugs to be delivered and released by a temperature-sensitive hydrogel include anti-thrombogenic agents, thrombolytic agents, anti-proliferative agents, anti-platelet agents, and chemotherapeutic agents. The drugs may be in any form capable of associating with the hydrogel and subsequently being released from the hydrogel by a triggering agent, including proteins, polypeptides, and DNA encoding such protein or polypeptide drugs.
Also within the invention is a method for triggering release of a drug from a hydrogel which is responsive to a specific wavelength of electromagnetic radiation. Preferably, the electromagnetic radiation required to trigger drug release has a wavelength in the visible range or in the ultraviolet range.
The hydrogel may contain a photo-sensitive compound capable of mediating a charge transfer, e.g., a compound containing a porphyrin ring. In preferred embodiments, drug release is triggered by exposure of the hydrogel to visible light and the hydrogel contains the photo-sensitive compound, chlorophyllin, e.g., a copolymer of N-isopropylacrylamide and chlorophyllin, which upon exposure to a visible wavelength of light causes the polymer to contract thereby triggering release of the drug. A light-triggered hydrogel may also contain a photo-sensitive dye, e.g., rhodamine.
In another embodiment, drug release is triggered by ultraviolet light which causes the hydrogel to swell, thereby allowing the drug to diffuse out of the hydrogel. For example, the hydrogel may contain a UV-sensitive compound such as leucocyanide or leucohydroxide, and the photo-sensitive hydrogel may be a copolymer of N-isopropylacrylamide and bis (4-dimethylamino)phenyl) (4-vinylphenyl)methyl leucocyanide.
The method for triggering release of a drug from a hydrogel which is responsive to electromagnetic radiation includes the following steps: providing a catheter constructed for insertion in a body lumen with a catheter shaft having (1) an expandable balloon portion coated with a electromagnetic radiation-sensitive hydrogel in which a drug has been immobilized and (2) an electromagnetic radiation-emitting fiber, e.g., a fiber optic device; introducing the catheter to the body lumen, at the point of desired drug application; expanding the balloon portion to engage the tissue; and exposing the hydrogel-coated balloon portion to the electromagnetic radiation.
Also within the invention is a method for triggering release of a drug from a hydrogel to a tissue from a balloon catheter containing a double membrane balloon portion of the catheter. At least a portion of the exterior surface of the expandable portion of the catheter is covered with a porous membrane positioned over the surface of the balloon portion to create a space into which a triggering agent or an additional dose of drug is introduced. The porous membrane is coated on its outer surface with a hydrogel which has been loaded with the drug to be delivered. The drug is immobilized in the hydrogel until released by a triggering agent, and the porous membrane is constructed to transmit the triggering agent from the space through openings in the membrane to the outer surface of the membrane in response to pressure applied by inflation of the balloon portion to compress the space. The space may be loaded with triggering agent. After the triggering agent has been delivered to the hydrogel and the drug released, the space may be re-filled with an additional dose of drug which, upon compression out of the space, contacts the hydrogel and replenishes it for the next triggered release.
Triggering drug-release from a drug-laden hydrogel using a double membrane balloon catheter includes the following steps: providing a catheter constructed for insertion in a body lumen having a catheter shaft with an expandable balloon portion and a porous membrane coated with a drug-containing hydrogel covering at least a portion of the balloon portion creating a space between the two membranes; preparing the balloon portion by introducing the triggering agent into the space; introducing the catheter to the body lumen at the point of desired drug application; and expanding the balloon portion to enable delivery of the triggering agent to the hydrogel by compression of the space.
To replenish the hydrogel coating with drug after a previous dose drug was released, the method requires the additional steps of: deflating the balloon portion after the expanding step; introducing into the space a solution of drug;, inflating the balloon portion to enable replenishment of the hydrogel with drug by squeezing the drug out of the space and into the hydrogel where the drug becomes immobilized until contacted with the triggering agent; and repeating the preparing and expanding steps.
In preferred embodiments, the drug is associated with the hydrogel by an ionic interaction, and the triggering agent, e.g., physiologic saline, optimally containing 0.1 to 0.2 M NaCl, increases the local ionic strength causing release of the drug from the hydrogel. The triggering agent administered to the hydrogel may also be a solution with a pH that induces a volume phase transition in the hydrogel, e.g., an expansion or contraction of the hydrogel, thereby triggering release of said drug. Altering the pH of the microenvironment of the hydrogel may also disrupt hydrogen bonds between the drug and the hydrogel, thus releasing the drug from the hydrogel. The pH of the solution is preferably greater than or equal to 7.5 and less than or equal to 7.3.
Other features and advantages of the invention will be apparent from the following description of the preferred embodiments thereof, and from the claims.